1. Field of the Invention
The invention relates to a recording apparatus which can be driven by a battery and, more particularly, to an ink jet recording apparatus.
2. Description of the Related Background Art
A printing recording apparatus of a printer, a facsimile apparatus, or the like is constructed in such a manner that an image comprising a dot pattern is recorded onto a recording sheet such as paper, thin plastics plate, or the like by driving an energy generating element of a recording head on the basis of image information which is transferred.
The above recording apparatus can be classified into an ink jet type, a wire dot type, a thermal type, and the like in dependence on recording methods. Among them, in the ink jet type (ink jet recording apparatus), a recording liquid (ink) droplet is discharged from a discharge port of the recording head and is allowed to fly and the droplet is deposited onto a material such as a paper or the like to be recorded, thereby recording.
In the ink jet recording apparatus of the type using heat as an ink droplet discharging energy, a discharge port is formed in the front surface of the recording head, that is, the surface which faces the material to be recorded and a liquid channel communicating from a common liquid chamber to the discharge port is formed in the recording head. A current is supplied to an electrothermal converting element such as a resistor or the like arranged on the liquid channel and the ink is heated, so that a state change which is accompanied with a sudden volume increase such as a generation of a bubble or the like due to a film boiling is caused in the ink, thereby discharging an ink droplet from the discharge port and allowing the ink droplet to fly. The above recording apparatus has excellent features such that a size of electrothermal converting element is extremely smaller than a piezoelectric transducing element which is used in a conventional ink jet recording apparatus, a large number of discharging ports can be installed as a multi-discharge port at a high density, a recording image of a high quality is derived, a recording speed is high, noises are low, and the like.
In the ink jet recording apparatus, if the ink discharge port of the recording head is opened toward the atmosphere for a long time in a state in which no recording is performed, a solvent component such as water, volatile organic solvent, or the like is evaporated into the atmosphere through the ink discharge port from the inks remaining in the ink discharge port and a portion around it because the ink is the water ink. Thus, viscosities of the inks remaining in the ink discharge port and a portion therearound increase and exceed a range suitable for the ink discharge. Therefore, a defective discharge such that no ink droplet is discharged even if a discharge signal has been applied just after the restart of the recording easily occurs.
On the other hand, if a vibration has been applied to the apparatus in a non-recording state, the ink leaks into the apparatus from the ink discharge port in spite of the fact that no discharge signal is applied. Therefore, problems such that the parts in the apparatus corrode and the like occur. Particularly, a small ink jet recording apparatus is often used as a portable apparatus. If the apparatus is moved or carried without sealing and closing the ink discharge port, a situation such that the ink which has leaked from the ink discharge port is scattered out of the apparatus can be also caused.
In the ink jet recording apparatus, therefore, a cap member is provided in order to isolate the ink discharge port from the atmosphere when no recording is performed. In the non-recording state, the cap member is driven by a motor or the like and is come into contact with the ink discharge port surface of the recording head. In the ink jet recording apparatus, particularly, in the small ink jet recording apparatus which is considered as a type for a portable use, it is necessary to certainly seal and close the ink discharge port by the cap member in the non-recording state because of the above reason.
Although the recording apparatus generally uses a commercially available power source as a main power source, in the case of a portable small recording apparatus, a two-source type comprising an AC adapter and a battery is frequently used.
In the case of driving the recording apparatus by a battery, however, an output voltage of the battery drops when a residual capacity of the battery decreases, so that it is difficult to drive each section in the apparatus. For instance, a situation such that the received recording information is lost if the function is suddenly stopped during the recording operation can be caused. In the case of the ink jet recording apparatus, a situation such that the ink discharge port of the recording head cannot be sealed and closed by the cap member can be caused.
In the case of driving the recording apparatus, particularly, the ink jet recording apparatus powered by a battery, it is necessary to use means for monitoring a battery capacity and means for protecting the apparatus when the battery capacity has decreased to a predetermined value or less.
In the electronic apparatus which can be driven by the battery, there is widely used a method of presuming the battery capacity by detecting the battery voltage by using a discharging characteristic such that the battery voltage drops with a decrease in battery capacity. In the ink jet recording apparatus as well, hitherto, the battery voltage is always detected and when it has dropped to a predetermined voltage, the lack of battery capacity is determined and the operation of the apparatus is interrupted and the lack of battery capacity is informed to the operator by a buzzer or a display device such as a lamp or the like.
The recording head is generally mounted on a carriage which is reciprocated in the horizontal direction by a carriage motor. The material to be recorded is conveyed in the direction perpendicular to the reciprocating directions of the carriage by a conveying roller which is driven by a sheet feed motor.
The conventional apparatuses, however, have the following drawbacks because the battery capacity is detected at an arbitrary timing.
Since a discharge current during the recording operation has a pulse waveform, the battery voltage also changes like a pulse in accordance with the discharge current. Further, the pulse waveform is set to an arbitrary pattern during the recording operation because an energy which is required to discharge an ink droplet and driving conditions of the carriage motor, sheet feed motor, and the like differ depending on an image to be recorded.
In the conventional apparatus, therefore, there is a technical subject such that a discriminating precision of the battery capacity deteriorates because the discharging conditions of the battery upon detection of the battery voltage change each time the battery voltage is detected. Therefore, there is a possibility such that the recording operation is continued in a state in which a lack of battery capacity cannot be detected. A situation such that the function of the apparatus is stopped during the recording of an image and the received recording information is extinguished can be caused. Or, in the case of the ink jet recording apparatus, a situation such that the ink discharge port of the recording head is left without being sealed and closed can be also caused.
To avoid such situations, it is necessary to select a discharge end voltage to be a relatively high value. However, the limited battery capacity cannot be effectively used and it is impossible to avoid a situation such that the driving time by the battery decreases.
The conventional apparatus in which the battery voltage is detected at an arbitrary timing, further, has the following drawbacks.
The battery voltage gradually rises just after the decrease in discharge current as in the case just after the operating mode has shifted from the recording mode to the standby mode. It takes about tens of seconds until the battery voltage is balanced although it differs in dependence on the discharging conditions before the operating mode is shifted to the standby mode. Therefore, the detection voltage value changes with the elapse of time in the standby mode and the discriminating precision of the battery capacity deteriorates. Thus, a situation such that the lack of battery capacity cannot be detected and the function of the apparatus is stopped can be also caused. To avoid such a situation, it is necessary to select the discharge end voltage to a relatively high value as mentioned above. However, the limited battery capacity cannot be effectively used and the driving time of the apparatus decreases.
Therefore, a method of detecting the battery voltage after waiting for a period of time which is required until the battery voltage is balanced is considered in the standby mode. According to the above method, however, even in the case where the recording information sent from a host apparatus just after the operating mode was shifted to the standby mode has been received as well, it is necessary to wait for a time until the battery voltage is balanced. Therefore, a throughput of the recording apparatus deteriorates.
On the contrary, a method of detecting the battery voltage only just after the operating mode was shifted to the standby mode is also considered. According to the above method, however, the following situation is also considered. That is, at a time point of the detection of the battery voltage, even if a battery capacity of a predetermined value or more remains, in the case where the standby mode had continued as it is for a long time such as 30 minutes, the battery capacity has already been smaller than the predetermined value when the recording information was received and the recording operation was started, so that the apparatus stops the function just after the start of the recording operation.
Furthermore, a method of a combination of the above two methods is also considered. That is, a battery voltage is first detected just after the operating mode was shifted to the standby mode and in the case where the standby mode has continued even after the elapse of a predetermined time which is required until the battery voltage is balanced, the battery voltage is always detected. According to such a combination method, however, a discharge end voltage is independently set for each of the case just after the operating mode was shifted to the standby mode and the case where the battery voltage approaches a balanced state, so that a burden of the software increases. In addition to the above problem, a change amount until the battery voltage reaches a balanced state differs due to a residual capacity of the battery or the discharging conditions before the operating mode is shifted to the standby mode. Therefore, it is actually impossible to balance and set the two or more discharge end voltage values so as not to cause a mutually contradictory judgment.